During program code reviews, understanding whether or not a specific piece of code is covered by tests can take considerable time and effort on the part of the engineer reviewing the code. The engineer needs to read both the code being tested and the tests, follow the code execution paths, and determine for each line of code whether or not it is executed. Such a process is not only difficult but also prone to error.
Alternatively, the code reviewer can ask the author of the code change to manually run one of the existing code-coverage calculators and report the results manually to the reviewer. Because this process involves at least two people performing manual steps, it can have a significant waiting period, especially if the reviewer and the author of the code change are geographically distant from one another.